e not allowed to access this font face.' ),
				array( 'status' => rest_authorization_required_code() )
			);
		}

		return true;
	}

	/**
	 * Validates settings when creating a font face.
	 *
	 * @since 6.5.0
	 *
	 * @param string          $value   Encoded JSON string of font face settings.
	 * @param WP_REST_Request $request Request object.
	 * @return true|WP_Error True if the settings are valid, otherwise a WP_Error object.
	 */
	public function validate_create_font_face_settings( $value, $request ) {
		$settings = json_decode( $value, true );

		// Check settings string is valid JSON.
		if ( null === $settings ) {
			return new WP_Error(
				'rest_invalid_param',
				__( 'font_face_settings parameter must be a valid JSON string.' ),
				array( 'status' => 400 )
			);
		}

		// Check that the font face settings match the theme.json schema.
		$schema             = $this->get_item_schema()['properties']['font_face_settings'];
		$has_valid_settings = rest_validate_value_from_schema( $settings, $schema, 'font_face_settings' );

		if ( is_wp_error( $has_valid_settings ) ) {
			$has_valid_settings->add_data( array( 'status' => 400 ) );
			return $has_valid_settings;
		}

		// Check that none of the required settings are empty values.
		$required = $schema['required'];
		foreach ( $required as $key ) {
			if ( isset( $settings[ $key ] ) && ! $settings[ $key ] ) {
				return new WP_Error(
					'rest_invalid_param',
					/* translators: %s: Name of the missing font face settings parameter, e.g. "font_face_settings[src]". */
					sprintf( __( '%s cannot be empty.' ), "font_face_setting[ $key ]" ),
					array( 'status' => 400 )
				);
			}
		}

		$srcs  = is_array( $settings['src'] ) ? $settings['src'] : array( $settings['src'] );
		$files = $request->get_file_params();

		foreach ( $srcs as $src ) {
			// Check that each src is a non-empty string.
			$src = ltrim( $src );
			if ( empty( $src ) ) {
				return new WP_Error(
					'rest_invalid_param',
					/* translators: %s: Font face source parameter name: "font_face_settings[src]". */
					sprintf( __( '%s values must be non-empty strings.' ), 'font_face_settings[src]' ),
					array( 'status' => 400 )
				);
			}

			// Check that srcs are valid URLs or file references.
			if ( false === wp_http_validate_url( $src ) && ! isset( $files[ $src ] ) ) {
				return new WP_Error(
					'rest_invalid_param',
					/* translators: 1: Font face source parameter name: "font_face_settings[src]", 2: The invalid src value. */
					sprintf( __( '%1$s value "%2$s" must be a valid URL or file reference.' ), 'font_face_settings[src]', $src ),
					array( 'status' => 400 )
				);
			}
		}

		// Check that each file in the request references a src in the settings.
		foreach ( array_keys( $files ) as $file ) {
			if ( ! in_array( $file, $srcs, true ) ) {
				return new WP_Error(
					'rest_invalid_param',
					/* translators: 1: File key (e.g. "file-0") in the request data, 2: Font face source parameter name: "font_face_settings[src]". */
					sprintf( __( 'File %1$s must be used in %2$s.' ), $file, 'font_face_settings[src]' ),
					array( 'status' => 400 )
				);
			}
		}

		return true;
	}

	/**
	 * Sanitizes the font face settings when creating a font face.
	 *
	 * @since 6.5.0
	 *
	 * @param string $value Encoded JSON string of font face settings.
	 * @return array Decoded and sanitized array of font face settings.
	 */
	public function sanitize_font_face_settings( $value ) {
		// Settings arrive as stringified JSON, since this is a multipart/form-data request.
		$settings = json_decode( $value, true );
		$schema   = $this->get_item_schema()['properties']['font_face_settings']['properties'];

		// Sanitize settings based on callbacks in the schema.
		foreach ( $settings as $key => $value ) {
			$sanitize_callback = $schema[ $key ]['arg_options']['sanitize_callback'];
			$settings[ $key ]  = call_user_func( $sanitize_callback, $value );
		}

		return $settings;
	}

	/**
	 * Retrieves a collection of font faces within the parent font family.
	 *
	 * @since 6.5.0
	 *
	 * @param WP_REST_Request $request Full details about the request.
	 * @return WP_REST_Response|WP_Error Response object on success, or WP_Error object on failure.
	 */
	public function get_items( $request ) {
		$font_family = $this->get_parent_font_family_post( $request['font_family_id'] );
		if ( is_wp_error( $font_family ) ) {
			return $font_family;
		}

		return parent::get_items( $request );
	}

	/**
	 * Retrieves a single font face within the parent font family.
	 *
	 * @since 6.5.0
	 *
	 * @param WP_REST_Request $request Full details about the request.
	 * @return WP_REST_Response|WP_Error Response object on success, or WP_Error object on failure.
	 */
	public function get_item( $request ) {
		$post = $this->get_post( $request['id'] );
		if ( is_wp_error( $post ) ) {
			return $post;
		}

		// Check that the font face has a valid parent font family.
		$font_family = $this->get_parent_font_family_post( $request['font_family_id'] );
		if ( is_wp_error( $font_family ) ) {
			return $font_family;
		}

		if ( (int) $font_family->ID !== (int) $post->post_parent ) {
			return new WP_Error(
				'rest_font_face_parent_id_mismatch',
				/* translators: %d: A post id. */
				sprintf( __( 'The font face does not belong to the specified font family with id of "%d".' ), $font_family->ID ),
				array( 'status' => 404 )
			);
		}

		return parent::get_item( $request );
	}

	/**
	 * Creates a font face for the parent font family.
	 *
	 * @since 6.5.0
	 *
	 * @param WP_REST_Request $request Full details about the request.
	 * @return WP_REST_Response|WP_Error Response object on success, or WP_Error object on failure.
	 */
	public function create_item( $request ) {
		$font_family = $this->get_parent_font_family_post( $request['font_family_id'] );
		if ( is_wp_error( $font_family ) ) {
			return $font_family;
		}

		// Settings have already been decoded by ::sanitize_font_face_settings().
		$settings    = $request->get_param( 'font_face_settings' );
		$file_params = $request->get_file_params();

		// Check that the necessary font face properties are unique.
		$query = new WP_Query(
			array(
				'post_type'              => $this->post_type,
				'posts_per_page'         => 1,
				'title'                  => WP_Font_Utils::get_font_face_slug( $settings ),
				'update_post_meta_cache' => false,
				'update_post_term_cache' => false,
			)
		);
		if ( ! empty( $query->posts ) ) {
			return new WP_Error(
				'rest_duplicate_font_face',
				__( 'A font face matching those settings already exists.' ),
				array( 'status' => 400 )
			);
		}

		// Move the uploaded font asset from the temp folder to the fonts directory.
		if ( ! function_exists( 'wp_handle_upload' ) ) {
			require_once ABSPATH . 'wp-admin/includes/file.php';
		}

		$srcs           = is_string( $settings['src'] ) ? array( $settings['src'] ) : $settings['src'];
		$processed_srcs = array();
		$font_file_meta = array();

		foreach ( $srcs as $src ) {
			// If src not a file reference, use it as is.
			if ( ! isset( $file_params[ $src ] ) ) {
				$processed_srcs[] = $src;
				continue;
			}

			$file      = $file_params[ $src ];
			$font_file = $this->handle_font_file_upload( $file );
			if ( is_wp_error( $font_file ) ) {
				return $font_file;
			}

			$processed_srcs[] = $font_file['url'];
			$font_file_meta[] = $this->relative_fonts_path( $font_file['file'] );
		}

		// Store the updated settings for prepare_item_for_database to use.
		$settings['src'] = count( $processed_srcs ) === 1 ? $processed_srcs[0] : $processed_srcs;
		$request->set_param( 'font_face_settings', $settings );

		// Ensure that $settings data is slashed, so values with quotes are escaped.
		// WP_REST_Posts_Controller::create_item uses wp_slash() on the post_content.
		$font_face_post = parent::create_item( $request );

		if ( is_wp_error( $font_face_post ) ) {
			return $font_face_post;
		}

		$font_face_id = $font_face_post->data['id'];

		foreach ( $font_file_meta as $font_file_path ) {
			add_post_meta( $font_face_id, '_wp_font_face_file', $font_file_path );
		}

		return $font_face_post;
	}

	/**
	 * Deletes a single font face.
	 *
	 * @since 6.5.0
	 *
	 * @param WP_REST_Request $request Full details about the request.
	 * @return WP_REST_Response|WP_Error Response object on success, or WP_Error object on failure.
	 */
	public function delete_item( $request ) {
		$post = $this->get_post( $request['id'] );
		if ( is_wp_error( $post ) ) {
			return $post;
		}

		$font_family = $this->get_parent_font_family_post( $request['font_family_id'] );
		if ( is_wp_error( $font_family ) ) {
			return $font_family;
		}

		if ( (int) $font_family->ID !== (int) $post->post_parent ) {
			return new WP_Error(
				'rest_font_face_parent_id_mismatch',
				/* translators: %d: A post id. */
				sprintf( __( 'The font face does not belong to the specified font family with id of "%d".' ), $font_family->ID ),
				array( 'status' => 404 )
			);
		}

		$force = isset( $request['force'] ) ? (bool) $request['force'] : false;

		// We don't support trashing for font faces.
		if ( ! $force ) {
			return new WP_Error(
				'rest_trash_not_supported',
				/* translators: %s: force=true */
				sprintf( __( 'Font faces do not support trashing. Set "%s" to delete.' ), 'force=true' ),
				array( 'status' => 501 )
			);
		}

		return parent::delete_item( $request );
	}

	/**
	 * Prepares a single font face output for response.
	 *
	 * @since 6.5.0
	 *
	 * @param WP_Post         $item    Post object.
	 * @param WP_REST_Request $request Request object.
	 * @return WP_REST_Response Response object.
	 */
	public function prepare_item_for_response( $item, $request ) {
		$fields = $this->get_fields_for_response( $request );
		$data   = array();

		if ( rest_is_field_included( 'id', $fields ) ) {
			$data['id'] = $item->ID;
		}
		if ( rest_is_field_included( 'theme_json_version', $fields ) ) {
			$data['theme_json_version'] = static::LATEST_THEME_JSON_VERSION_SUPPORTED;
		}

		if ( rest_is_field_included( 'parent', $fields ) ) {
			$data['parent'] = $item->post_parent;
		}

		if ( rest_is_field_included( 'font_face_settings', $fields ) ) {
			$data['font_face_settings'] = $this->get_settings_from_post( $item );
		}

		$context = ! empty( $request['context'] ) ? $request['context'] : 'view';
		$data    = $this->add_additional_fields_to_object( $data, $request );
		$data    = $this->filter_response_by_context( $data, $context );

		$response = rest_ensure_response( $data );

		if ( rest_is_field_included( '_links', $fields ) || rest_is_field_included( '_embedded', $fields ) ) {
			$links = $this->prepare_links( $item );
			$response->add_links( $links );
		}

		/**
		 * Filters the font face data for a REST API response.
		 *
		 * @since 6.5.0
		 *
		 * @param WP_REST_Response $response The response object.
		 * @param WP_Post          $post     Font face post object.
		 * @param WP_REST_Request  $request  Request object.
		 */
		return apply_filters( 'rest_prepare_wp_font_face', $response, $item, $request );
	}

	/**
	 * Retrieves the post's schema, conforming to JSON Schema.
	 *
	 * @since 6.5.0
	 *
	 * @return array Item schema data.
	 */
	public function get_item_schema() {
		if ( $this->schema ) {
			return $this->add_additional_fields_schema( $this->schema );
		}

		$schema = array(
			'$schema'    => 'http://json-schema.org/draft-04/schema#',
			'title'      => $this->post_type,
			'type'       => 'object',
			// Base properties for every Post.
			'properties' => array(
				'id'                 => array(
					'description' => __( 'Unique identifier for the post.', 'default' ),
					'type'        => 'integer',
					'context'     => array( 'view', 'edit', 'embed' ),
					'readonly'    => true,
				),
				'theme_json_version' => array(
					'description' => __( 'Version of the theme.json schema used for the typography settings.' ),
					'type'        => 'integer',
					'default'     => static::LATEST_THEME_JSON_VERSION_SUPPORTED,
					'minimum'     => 2,
					'maximum'     => static::LATEST_THEME_JSON_VERSION_SUPPORTED,
					'context'     => array( 'view', 'edit', 'embed' ),
				),
				'parent'             => array(
					'description' => __( 'The ID for the parent font family of the font face.' ),
					'type'        => 'integer',
					'context'     => array( 'view', 'edit', 'embed' ),
				),
				// Font face settings come directly from theme.json schema
				// See https://schemas.wp.org/trunk/theme.json
				'font_face_settings' => array(
					'description'          => __( 'font-face declaration in theme.json format.' ),
					'type'                 => 'object',
					'context'              => array( 'view', 'edit', 'embed' ),
					'properties'           => array(
						'fontFamily'            => array(
							'description' => __( 'CSS font-family value.' ),
							'type'        => 'string',
							'default'     => '',
							'arg_options' => array(
								'sanitize_callback' => array( 'WP_Font_Utils', 'sanitize_font_family' ),
							),
						),
						'fontStyle'             => array(
							'description' => __( 'CSS font-style value.' ),
							'type'        => 'string',
							'default'     => 'normal',
							'arg_options' => array(
								'sanitize_callback' => 'sanitize_text_field',
							),
						),
						'fontWeight'            => array(
							'description' => __( 'List of available font weights, separated by a space.' ),
							'default'     => '400',
							// Changed from `oneOf` to avoid errors from loose type checking.
							// e.g. a fontWeight of "400" validates as both a string and an integer due to is_numeric check.
							'type'        => array( 'string', 'integer' ),
							'arg_options' => array(
								'sanitize_callback' => 'sanitize_text_field',
							),
						),
						'fontDisplay'           => array(
							'description' => __( 'CSS font-display value.' ),
							'type'        => 'string',
							'default'     => 'fallback',
							'enum'        => array(
								'auto',
								'block',
								'fallback',
								'swap',
								'optional',
							),
							'arg_options' => array(
								'sanitize_callback' => 'sanitize_text_field',
							),
						),
						'src'                   => array(
							'description' => __( 'Paths or URLs to the font files.' ),
							// Changed from `oneOf` to `anyOf` due to rest_sanitize_array converting a string into an array,
							// and causing a "matches more than one of the expected formats" error.
							'anyOf'       => array(
								array(
									'type' => 'string',
								),
								array(
									'type'  => 'array',
									'items' => array(
										'type' => 'string',
									),
								),
							),
							'default'     => array(),
							'arg_options' => array(
								'sanitize_callback' => function ( $value ) {
									return is_array( $value ) ? array_map( array( $this, 'sanitize_src' ), $value ) : $this->sanitize_src( $value );
								},
							),
						),
						'fontStretch'           => array(
							'description' => __( 'CSS font-stretch value.' ),
							'type'        => 'string',
							'arg_options' => array(
								'sanitize_callback' => 'sanitize_text_field',
							),
						),
						'ascentOverride'        => array(
							'description' => __( 'CSS ascent-override value.' ),
							'type'        => 'string',
							'arg_options' => array(
								'sanitize_callback' => 'sanitize_text_field',
							),
						),
						'descentOverride'       => array(
							'description' => __( 'CSS descent-override value.' ),
							'type'        => 'string',
							'arg_options' => array(
								'sanitize_callback' => 'sanitize_text_field',
							),
						),
						'fontVariant'           => array(
							'description' => __( 'CSS font-variant value.' ),
							'type'        => 'string',
							'arg_options' => array(
								'sanitize_callback' => 'sanitize_text_field',
							),
						),
						'fontFeatureSettings'   => array(
							'description' => __( 'CSS font-feature-settings value.' ),
							'type'        => 'string',
							'arg_options' => array(
								'sanitize_callback' => 'sanitize_text_field',
							),
						),
						'fontVariationSettings' => array(
							'description' => __( 'CSS font-variation-settings value.' ),
							'type'        => 'string',
							'arg_options' => array(
								'sanitize_callback' => 'sanitize_text_field',
							),
						),
						'lineGapOverride'       => array(
							'description' => __( 'CSS line-gap-override value.' ),
							'type'        => 'string',
							'arg_options' => array(
								'sanitize_callback' => 'sanitize_text_field',
							),
						),
						'sizeAdjust'            => array(
							'description' => __( 'CSS size-adjust value.' ),
							'type'        => 'string',
							'arg_options' => array(
								'sanitize_callback' => 'sanitize_text_field',
							),
						),
						'unicodeRange'          => array(
							'description' => __( 'CSS unicode-range value.' ),
							'type'        => 'string',
							'arg_options' => array(
								'sanitize_callback' => 'sanitize_text_field',
							),
						),
						'preview'               => array(
							'description' => __( 'URL to a preview image of the font face.' ),
							'type'        => 'string',
							'format'      => 'uri',
							'default'     => '',
							'arg_options' => array(
								'sanitize_callback' => 'sanitize_url',
							),
						),
					),
					'required'             => array( 'fontFamily', 'src' ),
					'additionalProperties' => false,
				),
			),
		);

		$this->schema = $schema;

		return $this->add_additional_fields_schema( $this->schema );
	}

	/**
	 * Retrieves the item's schema for display / public consumption purposes.
	 *
	 * @since 6.5.0
	 *
	 * @return array Public item schema data.
	 */
	public function get_public_item_schema() {

		$schema = parent::get_public_item_schema();

		// Also remove `arg_options' from child font_family_settings properties, since the parent
		// controller only handles the top level properties.
		foreach ( $schema['properties']['font_face_settings']['properties'] as &$property ) {
			unset( $property['arg_options'] );
		}

		return $schema;
	}

	/**
	 * Retrieves the query params for the font face collection.
	 *
	 * @since 6.5.0
	 *
	 * @return array Collection parameters.
	 */
	public function get_collection_params() {
		$query_params = parent::get_collection_params();

		// Remove unneeded params.
		unset(
			$query_params['after'],
			$query_params['modified_after'],
			$query_params['before'],
			$query_params['modified_before'],
			$query_params['search'],
			$query_params['search_columns'],
			$query_params['slug'],
			$query_params['status']
		);

		$query_params['orderby']['default'] = 'id';
		$query_params['orderby']['enum']    = array( 'id', 'include' );

		/**
		 * Filters collection parameters for the font face controller.
		 *
		 * @since 6.5.0
		 *
		 * @param array $query_params JSON Schema-formatted collection parameters.
		 */
		return apply_filters( 'rest_wp_font_face_collection_params', $query_params );
	}

	/**
	 * Get the params used when creating a new font face.
	 *
	 * @since 6.5.0
	 *
	 * @return array Font face create arguments.
	 */
	public function get_create_params() {
		$properties = $this->get_item_schema()['properties'];
		return array(
			'theme_json_version' => $properties['theme_json_version'],
			// When creating, font_face_settings is stringified JSON, to work with multipart/form-data used
			// when uploading font files.
			'font_face_settings' => array(
				'description'       => __( 'font-face declaration in theme.json format, encoded as a string.' ),
				'type'              => 'string',
				'required'          => true,
				'validate_callback' => array( $this, 'validate_create_font_face_settings' ),
				'sanitize_callback' => array( $this, 'sanitize_font_face_settings' ),
			),
		);
	}

	/**
	 * Get the parent font family, if the ID is valid.
	 *
	 * @since 6.5.0
	 *
	 * @param int $font_family_id Supplied ID.
	 * @return WP_Post|WP_Error Post object if ID is valid, WP_Error otherwise.
	 */
	protected function get_parent_font_family_post( $font_family_id ) {
		$error = new WP_Error(
			'rest_post_invalid_parent',
			__( 'Invalid post parent ID.', 'default' ),
			array( 'status' => 404 )
		);

		if ( (int) $font_family_id <= 0 ) {
			return $error;
		}

		$font_family_post = get_post( (int) $font_family_id );

		if ( empty( $font_family_post ) || empty( $font_family_post->ID )
		|| 'wp_font_family' !== $font_family_post->post_type
		) {
			return $error;
		}

		return $font_family_post;
	}

	/**
	 * Prepares links for the request.
	 *
	 * @since 6.5.0
	 *
	 * @param WP_Post $post Post object.
	 * @return array Links for the given post.
	 */
	protected function prepare_links( $post ) {
		// Entity meta.
		return array(
			'self'       => array(
				'href' => rest_url( $this->namespace . '/font-families/' . $post->post_parent . '/font-faces/' . $post->ID ),
			),
			'collection' => array(
				'href' => rest_url( $this->namespace . '/font-families/' . $post->post_parent . '/font-faces' ),
			),
			'parent'     => array(
				'href' => rest_url( $this->namespace . '/font-families/' . $post->post_parent ),
			),
		);
	}

	/**
	 * Prepares a single font face post for creation.
	 *
	 * @since 6.5.0
	 *
	 * @param WP_REST_Request $request Request object.
	 * @return stdClass Post object.
	 */
	protected function prepare_item_for_database( $request ) {
		$prepared_post = new stdClass();

		// Settings have already been decoded by ::sanitize_font_face_settings().
		$settings = $request->get_param( 'font_face_settings' );

		// Store this "slug" as the post_title rather than post_name, since it uses the fontFamily setting,
		// which may contain multibyte characters.
		$title = WP_Font_Utils::get_font_face_slug( $settings );

		$prepared_post->post_type    = $this->post_type;
		$prepared_post->post_parent  = $request['font_family_id'];
		$prepared_post->post_status  = 'publish';
		$prepared_post->post_title   = $title;
		$prepared_post->post_name    = sanitize_title( $title );
		$prepared_post->post_content = wp_json_encode( $settings );

		return $prepared_post;
	}

	/**
	 * Sanitizes a single src value for a font face.
	 *
	 * @since 6.5.0
	 *
	 * @param string $value Font face src that is a URL or the key for a $_FILES array item.
	 * @return string Sanitized value.
	 */
	protected function sanitize_src( $value ) {
		$value = ltrim( $value );
		return false === wp_http_validate_url( $value ) ? (string) $value : sanitize_url( $value );
	}

	/**
	 * Handles the upload of a font file using wp_handle_upload().
	 *
	 * @since 6.5.0
	 *
	 * @param array $file Single file item from $_FILES.
	 * @return array|WP_Error Array containing uploaded file attributes on success, or WP_Error object on failure.
	 */
	protected function handle_font_file_upload( $file ) {
		add_filter( 'upload_mimes', array( 'WP_Font_Utils', 'get_allowed_font_mime_types' ) );
		// Filter the upload directory to return the fonts directory.
		add_filter( 'upload_dir', '_wp_filter_font_directory' );

		$overrides = array(
			'upload_error_handler' => array( $this, 'handle_font_file_upload_error' ),
			// Not testing a form submission.
			'test_form'            => false,
			// Only allow uploading font files for this request.
			'mimes'                => WP_Font_Utils::get_allowed_font_mime_types(),
		);

		// Bypasses is_uploaded_file() when running unit tests.
		if ( defined( 'DIR_TESTDATA' ) && DIR_TESTDATA ) {
			$overrides['action'] = 'wp_handle_mock_upload';
		}

		$uploaded_file = wp_handle_upload( $file, $overrides );

		remove_filter( 'upload_dir', '_wp_filter_font_directory' );
		remove_filter( 'upload_mimes', array( 'WP_Font_Utils', 'get_allowed_font_mime_types' ) );

		return $uploaded_file;
	}

	/**
	 * Handles file upload error.
	 *
	 * @since 6.5.0
	 *
	 * @param array  $file    File upload data.
	 * @param string $message Error message from wp_handle_upload().
	 * @return WP_Error WP_Error object.
	 */
	public function handle_font_file_upload_error( $file, $message ) {
		$status = 500;
		$code   = 'rest_font_upload_unknown_error';

		if ( __( 'Sorry, you are not allowed to upload this file type.' ) === $message ) {
			$status = 400;
			$code   = 'rest_font_upload_invalid_file_type';
		}

		return new WP_Error( $code, $message, array( 'status' => $status ) );
	}

	/**
	 * Returns relative path to an uploaded font file.
	 *
	 * The path is relative to the current fonts directory.
	 *
	 * @since 6.5.0
	 * @access private
	 *
	 * @param string $path Full path to the file.
	 * @return string Relative path on success, unchanged path on failure.
	 */
	protected function relative_fonts_path( $path ) {
		$new_path = $path;

		$fonts_dir = wp_get_font_dir();
		if ( str_starts_with( $new_path, $fonts_dir['path'] ) ) {
			$new_path = str_replace( $fonts_dir, '', $new_path );
			$new_path = ltrim( $new_path, '/' );
		}

		return $new_path;
	}

	/**
	 * Gets the font face's settings from the post.
	 *
	 * @since 6.5.0
	 *
	 * @param WP_Post $post Font face post object.
	 * @return array Font face settings array.
	 */
	protected function get_settings_from_post( $post ) {
		$settings   = json_decode( $post->post_content, true );
		$properties = $this->get_item_schema()['properties']['font_face_settings']['properties'];

		// Provide required, empty settings if needed.
		if ( null === $settings ) {
			$settings = array(
				'fontFamily' => '',
				'src'        => array(),
			);
		}

		// Only return the properties defined in the schema.
		return array_intersect_key( $settings, $properties );
	}
}